If you get a "database not found" or "unable to open database" message, ensure that your database files are in the place configured on the system page. If they are, and you still have problems, try restoring a recent backup. You may also be able to recover database files with a Paradox table file repair utility, but don't try this unless you are familiar with such a tool and know the consequences of using it.
Running out of disk space may cause strange errors. Ensure that you have enough disk space on the drive where your database files reside.
If you run into problems with the way files are sorted, check for consistency in the way data was entered. For example, if someone interchanged the letter "l" and the numeral "1" or the letter "O" and the numeral "0", you could get some really strange results. Likewise, city names must be entered consistently. "Colorado Springs" and "Colo Springs" are two totally different cities, as far as DTN is concerned.